Digital video/audio recording/playback apparatuses adopting disc mediums and/or semiconductor mediums have become popular. In this relation, there have been needs for inexpensively adding postrecording capability to the digital video/audio recording/playback apparatuses adopting disc mediums, as in the case of apparatuses adopting tape mediums. The postrecording capability allows for the addition of information (audio and graphic information in particular) to audio and/or video data that have been recorded.
Being different from the tape mediums, the disc mediums characteristically allow for nondestructive editing, i.e. nonlinear editing. That is, the nondestructive editing capability or nonlinear editing capability allows any sections of an AV stream recorded on a disc to be played back in an optional order, without moving or copying the AV stream. Not just changing the order of playback, the aforesaid capability makes it possible to produce different kinds of user programs from a single set of scenes, i.e. makes it possible to share a single set of scenes between a plurality of user programs. In response to this, the users' demand to perform postrecording corresponding to each user program.
For example, it has been demanded to add, in a program A, background music to a particular scene, meanwhile, in a program B, to add narration to the same scene. To meet such a demand, Japanese Laid-Open Patent Application No. 2002-373480 (published on Dec. 26, 2002) proposes to provide information for managing postrecording area allocation. With this, in a case where a plurality of user programs carry out the postrecording, it is possible to avoid unintentional overwriting to a scene shared between the different user programs.
FIG. 27 shows a recording format of a disc disclosed in Japanese Laid-Open Patent Application No. 2002-373480. A recording area on the disc is composed of a series of ECC (Error Correcting Code) blocks. The ECC block is the smallest unit for encoding. Parity for error correction is added to data, so that the encoding is performed. To read data from the disk, the reading error correction is carried out in units of the ECC blocks, and then required data is obtained.
On the other hand, to rewrite data on the disc, the data is read out in units of the ECC blocks, a necessary part of the error-corrected data is rewritten, an error code is added again, and the data is recorded onto the disc.
In the ECC block, video data and audio data are arranged in the following order: postrecording data block, original audio block, and original video block. Each of these blocks includes postrecording data, original audio data, and original video data, which correspond to a more or less identical period of time.
It is noted that the original audio block and original video block are termed “original block”. To allow the recording of an original program (video picture before the recording of postrecording data), dummy data has been recorded in the postrecording data block.
The recording of postrecording data involves data writing to the postrecording data block. In this relation, an area, of the postrecording data block, to which the recording has been done is regarded as an allocated area, while the remaining areas of the postrecording data block are regarded as non-allocated areas. Management information in the original program individually manages these types of areas. Referring to the management information, it is possible to prevent postrecording data from being overwritten when different user programs are used. In a case where new postrecording data is recorded, management information of each area is rewritten.
However, in the above-described arrangement, in a case where a user program is deleted, it is difficult to delete unnecessary postrecording data corresponding to the user program to be deleted, and to effectively reutilize the freed postrecording data block area. This is because of the reason below.
In a case where a scene is shared between a plurality of user programs, it is not easy to delete each piece of postrecording data, because each piece of data may be referred to by the plurality of user programs.
That is to say, when deleting a user program and also postrecording data referred to by the user program, the postrecording data must be only referred to by that user program to be deleted, i.e. the data is required not to be shared by another user program.
In the conventional art, after the deletion of a user program, it is necessary to check the management information of all user program, to determine that postrecording data which was referred to by the deleted program is not referred to by any other user programs and hence the data can be deleted. The checking of the management information causes trouble in terms of processing time, particularly in a case of optical discs that requires long seek time.